Paper 2

• Linear Search

  • algorithm that moves through every item one at a time until it finds the item it's looking for
• Binary Search

  • divide and conquer algorithm
  • splits list into smaller lists until it finds the item its searching for
• Bubble Sort

  • passes through list, evaluating pairs of items and making sure the larger value is above the smaller one
• Queues

  • first in first out (FIFO)
  • often represented as arrays
  • make use of two pointers
  • front holds position of first element
  • back stores next available space
  • operations carried out on queues are similar to those in stacks
• Stacks

  • first in last out (FILO)
  • implemented as an array
  • single pointer that keeps track of top of stack
  • points to element currently at the top
  • initialised at -1, first element is position 0
• Waterfall Lifecycle

  • stages completed in sequence, start to finish
  • clear structure makes it easy to follow
  • to make a change programmers must revisit all stages between
  • low user involvement
• Agile Methodologies

  • aim to improve flexibility of SDLCs
  • adapt quickly to changes in user requirements
  • different sections are developed in parallel so can be at different stages simultaneously
  • working prototype delivered early on and improved in iterative manner
  • less focus on documentation
  • user satisfaction prioritised
• Extreme Programming

  • agile model
  • development team is a pair of programmers and representative end-user
  • user stories used to determine system requirements
  • produces high-quality code and highly usable software
  • programmers work no longer than 40 hours a week
  • hard to produce high quality documentation
• Spiral Model

  • manages risk-heavy projects
  • project terminated if too risky
  • specialised risk-assessors must be hired - expensive
• Spiral Model - Stages

  • analysing system requirements
  • pinpointing/mitigating risks
  • development, testing and implementation
  • evaluating to inform the next iteration
• Rapid Application Development

  • iterative methodology which uses partially functioning prototypes
  • user requirements gathered using focus group
  • incomplete version of solution given to user to trial
  • user feedback used to generate improved prototype
  • final prototype matches user requirements fully
  • used where user requirements are incomplete or unclear at start
  • code may be inefficient
• Waterfall - Advantages

  • straightforward to manage
  • clearly documented
• Waterfall - Disadvantages

  • lack of flexibility
  • no risk analysis
  • limited user involvement
• Waterfall - Uses

  • static, low risk projects that need little user input
• Agile - Advantages

  • high quality code
  • flexible to changing requirements
  • regular user input
• Agile - Disadvantages

  • poor documentation
  • interaction between user and programmer
• Agile - Uses

  • small to medium projects with unclear initial requirements
• Extreme - Advantages

  • high quality code
  • constant user involvement - high usability
• Extreme - Disadvantages

  • high cost of two people working together on one project
  • teamwork is essential
  • end-user needs to be present
• Extreme - Uses

  • small to medium projects with unclear initial requirements
  • require excellent usability
• Spiral - advantages

  • thorough risk-analysis
  • caters to changing user needs
  • prototypes produced throughout
• Spiral - disadvantages

  • expensive (hiring risk assessors)
  • lack of focus on code efficiency
  • high costs due to constant prototyping
• Spiral - uses

  • large, risk-intensive projects with a high budget
• RAD - advantages

  • caters to changing user requirements
  • highly usable finished product
  • focus on core features, reducing development time
• RAD - disadvantages

  • poorer quality documentation
  • fast pace and late changes can reduce code quality
• RAD - uses

  • small to medium, low budget projects with short time frames
• Alpha Testing

  • carried out in-house by software development teams
  • bugs are pinpointed and fixed
• Beta Testing

  • carried out by end users
  • feedback from users inform next stage of development
• Whitebox testing

  • carried out by software development teams
  • internal structure of program is recognised
  • all possible routes through program are tested
• Blackbox Testing

  • testers are not aware of internal structure of the software
  • test plan traces through inputs and outputs
• Local Variables

  • can only be accessed within subroutine where they were defined
  • multiple local variables with the same name can exist in different subroutines
  • they're deleted once the subroutine ends
  • using local variables ensures subroutines are self-contained
• Global Variables

  • can be accessed across whole program
  • useful for values that need to be used by multiple parts of the program
  • danger of being unintentionally edited
  • not deleted until program terminates - requires more memory
• Modular Programming

  • splits large, complex programs into smaller, self-contained modules
  • easier to divide tasks between a team and manage projects
  • simplifies process of testing and maintenance as each component can be deal with individually
  • improves reusability of components
• Top-down Design/Stepwise Refinement

  • technique used to modularise programs
  • problem is broken into sub-problems until each is represented as an individual, self contained module that performs a certain task
  • modules form blocks of code called subroutines
• Passing by Value

  • copy of the value is passed to subroutine and discarded at the end
  • value outside subroutine remains unaffected
• Passing by Reference

  • address of parameter is given to subroutine
  • value of parameter will be updated at given address
• Integrated Development Environment (IDE)

  • provides a set of tools to make it easier for programmers to write, develop and debug code
• IDE - Features

  • stepping
  • variable watch
  • breakpoint
  • source code editor
  • debugging tools
• Software Development Life Cycles (SDLCs) - stages

  • analysis
  • design
  • development
  • testing
  • implementation
  • evaluation
  • maintenance